JPH0346316B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lithographic printing support and a method for producing the same;
In particular, the present invention relates to an aluminum type plate for lithographic printing and a method for manufacturing the same. Conventionally, aluminum plates have been widely used as supports for lithographic printing.Aluminum plates have been used to improve adhesion with the photosensitive layer provided thereon, and also to improve the non-image area ( The surface of the aluminum plate is roughened for the purpose of improving water retention in the exposed area of the support (the area that receives dampening water and repels oil-based ink used during printing). It is customary. This surface roughening treatment is called graining and is an essential step in the preparation of supports for lithographic printing plates. This graining can be achieved by mechanical surface roughening methods such as ball grain, wire grain, brush grain, and blast grain, electrolytic surface roughening method that electrochemically etches in acid or neutral aqueous solution, and special surface roughening methods. A chemical surface roughening method is known in which aluminum alloy material is chemically etched with acid or alkali. “Basics of Lithographic Printing” published by Printing Jihosha
(Author Kenichi Sugiyama, published December 1, 1965) No. 35-37
The page provides a general explanation of the graining method, and specifically describes a method of mechanically roughening the surface using an abrasive thriller. Printed Magazine, July 1963 issue, pages 2-4, ``Overview of Alumite Lithography'' (Author: Michi Sano) describes a lithographic printing plate that is electrolytically roughened by alternating current using hydrochloric acid or nitric acid, and then treated with anodic acid. The manufacturing method is described. Japanese Patent Publication No. 54-42284 describes a method for producing a lithographic printing plate in which an aluminum plate containing 1.6-2.5% manganese is chemically roughened with an alkali. On the other hand, a composite graining method in which these known surface roughening methods are appropriately combined is also well known. for example,
U.S. Patent No. 2,344,510 discloses that after mechanical roughening, electrical roughening is performed using hydrochloric acid etc. to form grains on the surface in a superimpose manner, and then the anode A method for producing a support for a lithographic printing plate that is subjected to an oxidation treatment is described. In addition, Tokko Akira
57-16918, after mechanical roughening,
A method for producing a support for a lithographic printing plate is described, which comprises chemically etching with an acid or alkali, followed by electrochemical roughening, and then anodizing. Furthermore, in Japanese Patent Application Laid-open No. 56-28893,
By sequentially performing mechanical roughening, chemical etching, and electrochemical roughening using an alternating waveform current in an acidic electrolyte, a lithographic printing plate support having a grain structure consisting of plateaus and pits on the aluminum surface was prepared. The manufacturing method is described. The present inventors have discovered that the shape of minute irregularities observed when the surface of a roughened aluminum support is magnified 2000 to 5000 times has an extremely large effect on printing performance as a lithographic printing support, as described below. It was discovered that (1) Strengthen the adhesion between the image layer and the support to improve printing durability. (2) In the same manner as in (1) above, the adhesion of the fine halftone dot image of about 1 to 5% to the support from the development process to the printing process is strengthened, and the tone reproducibility is improved. (3) Strengthen the adhesion of the hydrophilic coating layer (eg, gum arabic) to the non-image area and improve hydrophilicity. (4) Improve water retention in non-image areas. The inventors of the present invention focused on this fine uneven structure and conducted repeated observations and experiments, and as a result, they came to the following considerations and conclusions. (a) Generally, a grained rough surface has a large roughness structure (primary structure) and a small roughness structure (secondary structure).
The minute irregularities having the above-mentioned effect originate from a secondary structure. (b) When mechanically roughening the surface, it is possible to increase or decrease the secondary structure by selecting the particle size of the abrasive used and carefully setting the processing conditions. This idea was introduced in Japanese Patent Publications No. 54-42282 and No. 54-42283, in which aluminum plates for offset printing are mechanically roughened using two types of abrasives with different particle sizes using a wet blasting method. It is disclosed as a manufacturing method. However, since abrasives, aluminum grinding chips, etc. usually remain on the mechanically roughened surface, blackening of the appearance due to these residual components, especially when printing plates are made by anodizing, Problems such as stains occurring during printing. (c) In order to solve the above problem,
As described in Publication No. 33444, chemical etching with acid or alkali or
The method described in Japanese Patent No. 19279, in which electrochemical etching in phosphoric acid is performed followed by anodic oxidation, is effective. However, since the secondary structure disappears in the etching process, new problems arise in that the surface properties imparted by the grainy grains are deteriorated and water retention and printing durability are reduced. (d) Similarly, formation of a double structure is observed in electrochemical roughening. For example, Sumitomo Light Metal Technical Report
Vol.15, No.2, April 1974 “The Process for
the Production of Electrolytically Etched
According to the experiments of the present inventors, the average surface roughness (Ra = 0.6μ) using an electrolyte mainly composed of hydrochloric acid and a commercial alternating current.
It required an amount of electricity of 1000-1500 coulombs/dm ² . Immediately after electrolysis, the surface is completely covered with an insoluble residue called smut, which is difficult to remove with normal washing with water or brushing.
As described in Japanese Patent No. 28123, it was necessary to etch the surface using an alkali. As a result, the secondary structure existed on the rough surface that was carefully and lightly etched, but when the etching amount was slightly exceeded, the secondary structure disappeared, and as a result, as in (c), the water retention There was a problem that hydrophilicity decreased. (e) Many attempts have been proposed to add various additives to the hydrochloric acid agent to suppress coarsening of the primary structure and promote the formation of fine secondary structures. Products containing nitric acid, chromic acid, and hydrofluoric acid as additives (Special Publication Act 1977-
28123), those containing amines, aldehydes, and nonionic surfactants as additives (Special Publication No. 1973-
Additives such as those using boric acid as an additive (No. 7081), those using boric acid as an additive (French Patent No. 2110257), and those using phosphoric acid as an additive (US Pat. No. 3,887,447) are known so far. In particular, in U.S. Pat. No. 3,887,447,
The authors mention the influence of sulfate ions as a trace impurity present in the electrolyte as a factor that inhibits the uniform formation of fine pits, and state that the presence of about 10-15 ppm of sulfate ions will result in uniform coarse pits, and will improve this. It is interesting that the addition of phosphoric acid is proposed as a means. (f) The inventors are confident that an electrolytic solution mainly composed of nitric acid is advantageous compared to hydrochloric acid in terms of focusing on fine secondary structures and forming them uniformly and efficiently on the surface. It came to this. The reason for this is that surfaces electrolytically roughened using an electrolyte mainly composed of nitric acid have less surface residue (smut) compared to hydrochloric acid, and therefore the residue can be removed by a relatively mild post-treatment. It is. This has the advantage that the grains obtained by electrolytic surface roughening are less likely to be destroyed. However, the rough surface structure obtained with a nitric acid-only electrolyte using commercial alternating current has an irregular and non-uniform arrangement including giant pits, so a uniform surface structure with a predetermined surface roughness necessary for a printing plate cannot be obtained. I had a problem with not being able to get it. (g) In addition, Japanese Patent Publication No. 1976-764 also describes protective colloids based on lignin, aromatic aldehydes,
A method for obtaining a fine rough surface structure by adding aromatic ketones to nitric acid is described. However, according to the results of additional tests conducted by the present inventor, the effects of these methods did not reach the desired effect of the present inventor and were insufficient. As a result of intensive research, the inventors of the present invention have found that the above problem can be achieved when a very limited range of nitrate radicals is allowed to coexist with an electrolytic solution mainly composed of nitric acid. This fact is extremely surprising considering that US Pat. No. 3,887,447 states that the coexistence of sulfate ions has an adverse effect. According to the present invention, as will be explained in detail below, a pit structure having a characteristic shape can be obtained,
Because of this shape characteristic, extremely favorable effects are exhibited in terms of printing performance (printing durability, resistance to staining). (1) The pits obtained by this method are circular and have individual independent structures, and have an opening diameter of 0.3 to 8 microns. (2) When electrochemical surface roughening is performed using this method using an alternating waveform current and the ratio of the amount of electricity at the cathode to the amount of electricity at the anode is in the range of 0.4 to 1.25, a uniformly roughened surface with no uneven distribution of giant pits can be obtained. surface roughness of 0.8 at 2000 coulombs/ ^dm2
It was possible to create a uniform grain with micron diameter. Incidentally, in the case of using nitric acid alone, an irregular rough surface with unevenly distributed giant pits was formed from around 500 coulombs/dm ² , and it was difficult to roughen the surface and create a uniform rough surface structure of 0.5 microns or more. (3) Using this method, an alternating waveform current is used, the amount of electricity at the anode does not exceed 2000 coulombs, the voltage is 5 to 50 V, the current density is in the range of 10 to 100 A/ ^dm2 , and the amount of electricity at the cathode is divided by the amount of electricity at the anode. Hourly electricity amount = 0.4
The bit structure described in (1) above was distributed in a superimposed manner as a secondary structure on a roughened surface that had been mechanically and/or chemically roughened to a predetermined surface roughness in the range of ~1.25. The rough surface with secondary structure showed the best results in printability. The details will be explained in Examples below. (4) Another noteworthy effect in (3) above is that the density of the pit structure can be controlled by the concentration of added nitrate radicals, and this fact is unexpected and extremely surprising. It is. Figure 1 shows nitric acid alone electrolyte (nitric acid concentration: 7
g/) and the alternating waveform current (cathode electricity quantity/
This figure shows the results of electrolytic surface roughening using anode electricity amount: 0.8). In the figure, the horizontal axis shows the amount of electricity applied (coulomb/dm ² of electricity at the time of anode), and the vertical axis shows the reflection density of the obtained roughened aluminum surface. Figure 5A, Figure 5B, Figure 5C
The figures are scanning electron micrographs (hereinafter referred to as SEM) of the surfaces of the samples at points A, B, and C in Figure 1, respectively, magnified 1500 times. From Figures 1, 5A, 5B, and 5C, the density of pits with an opening diameter of 0.3 to 8 microns increases in proportion to the amount of electricity, and the density of reflection on the rough surface increases accordingly. is understood. Figure 2 is a graph showing, as an example, the relationship between the amount of sulfuric acid added and the reflection density when sulfuric acid is added to nitric acid under a certain amount of electricity, and the horizontal axis is the amount of sulfuric acid added (unit: ppm ), and the vertical axis shows the reflection density of the roughened aluminum surface obtained. The conditions for electrochemical surface roughening at this time were: nitric acid concentration: 7 g/, quantity of electricity at anode: 175 coulombs/dm ² , quantity of electricity at cathode: 145 coulombs/dm ² , quantity of electricity at cathode/quantity of electricity at anode. :
It was 0.8. Figure 6A, Figure 6B, Figure 6C,
Figure 6D shows the sulfuric acid concentration οppm, 100ppm,
These are SEM images of roughened surfaces corresponding to 1000ppm and 5000ppm. It can be seen from this that the micro pit density increases with a specific range of sulfuric acid concentration despite the same amount of input electricity. Similar results can be obtained by arbitrarily changing the amount of electricity applied. The concentration of useful sulfate radicals can vary depending on the concentration of nitric acid, the alternating waveform current density, and the amount of coexisting aluminum nitrate.
It ranges from 50 to 4000 ppm. If it exceeds 5000 ppm, the etching reaction will be inhibited due to the formation of a passive film. Furthermore, since the concentration of sulfate ions normally present in well water is 2 to 25 ppm, it is difficult to control the concentration below 25 ppm. As the source of the sulfuric acid radical, in addition to sulfuric acid, its potassium salt, sodium salt, etc. can be used. Among these, sulfuric acid is preferred. Nitric acid concentration is
Can be used in the range of 1000 to 40000ppm,
Also, the unavoidable components that coexist are AL, CO ₃ ^-2 ,
There are Na, Fe, and Si, but among these, aluminum has a 1000~
Can be used in the range of 20000ppm. (5) As illustrated in Figure 2, the behavior when sulfuric acid is added to nitric acid can be broadly classified into three types. first,
0~800ppm is the area where the pit density increases as the amount added, then 800~3000ppm
is a region where a constant pit density is maintained insensitively to the amount added, and 3000 ppm to 4000 ppm corresponds to a region where the equilibration effect decreases as the amount of addition increases. Therefore, in the first region, it is possible to save the input electricity amount by controlling the concentration of sulfate radicals. In addition, in the second region, which is insensitive to the concentration of sulfate radicals, under manufacturing conditions with a wide variation degree, printing with excellent printing performance due to the surface shape having the characteristics described in (1) to (3) above is possible. It becomes possible to manufacture plates. The aluminum plate used in the present invention includes pure aluminum and aluminum alloy plate. Various aluminum alloys can be used,
For example, alloys of aluminum and metals such as silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth, and nickel are used. Specific examples of aluminum alloys are shown in the table below. The units of numbers in the table are % by weight, with the remainder being aluminum.

In addition to some iron and titanium, these compositions also contain negligible amounts of other unlisted impurities. In a preferred embodiment of the present invention, the aluminum plate is first mechanically roughened, but prior to this, the aluminum plate is first roughened to remove rolling oil from the aluminum surface and to reveal a clean aluminum surface. It is common practice to carry out processing. In order to remove rolling oil, treatment with a solvent such as triclene, a surfactant, etc. is used. In order to obtain a clean surface, etching with an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide is widely used. However, according to the present invention, pretreatment prior to mechanical surface roughening can be omitted, except in cases where a particularly large amount of rolling oil is attached. Any of the mechanical surface roughening methods described above may be used in the method of the present invention. Such mechanically grained aluminum plates are then chemically etched.
This treatment is performed to remove abrasives, aluminum chips, etc. that have become ingrained during mechanical graining, and to effectively perform the electrochemical roughening that is applied afterwards. This is done by immersing an aluminum plate in an aqueous solution. Specific examples of the acid or alkaline aqueous solution include acids such as hydrofluoric acid, fluorozirconic acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, and sodium hydroxide, potassium hydroxide, sodium triphosphate, sodium aluminate, and silicic acid. An alkaline aqueous solution such as sodium or sodium carbonate is used. These acid or alkali aqueous solutions can be used alone or in combination of two or more. In the etching process of the present invention, it is preferable to process the aluminum plate under conditions such that aluminum is etched preferably in the range of 2 to 12 g/m ² . By etching the surface of a brush-grained aluminum plate within the above-mentioned range, it is possible to create uniform microscopic grains with a large average roughness, which is the object of the present invention. When an aluminum surface is chemically treated with an aqueous alkali solution, an insoluble residue, ie, smut, is formed on the surface. This smut can be removed with phosphoric acid, nitric acid, chromic acid or mixtures thereof. In the present invention, it is desirable that the aluminum surface to be electrochemically treated be a clean surface without smut, but this may be omitted if, for example, the electrolyte is an acid and has a desmut action. The aluminum plate thus treated is subsequently subjected to electrochemical roughening as described above. It is preferable to form an anodic oxide film on the surface of the aluminum support thus obtained. As an electrolyte, in addition to sulfuric acid, for example, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, etc., or a combination of two or more of these acids can be used in an aqueous or non-aqueous solution, and when an electric current is passed using aluminum as an anode, aluminum supports An anodic oxide film can be formed on the body surface. The processing conditions for anodic oxidation vary depending on the electrolyte used, so they cannot be determined unconditionally, but in general, the concentration of the electrolyte is 1 to 80% by weight, and the temperature of the solution is 5 to 70%.
°C, current density 0.5~60 ampere/ ^dm2 , voltage 1~
A range of 100V and electrolysis time of 30 seconds to 50 minutes is appropriate.
More specifically, the anodizing treatment conditions as shown in the table below are preferable.

[Table] A photosensitive lithographic printing plate can be obtained by coating a photosensitive substance on the support thus obtained. Any photosensitive substance can be used as long as its solubility or swelling ability in a developer changes before and after exposure. Preferred examples include diazo compounds, such as photosensitive compositions consisting of diazo resin and silica (Japanese Patent Application Laid-Open No. 47-34404), photosensitive compositions consisting of poly(hydroxyethyl methacrylate) and diazo resin, and diazo resin and soluble polyamide. Photosensitive compositions consisting of resin (US Pat. No. 3,751,257), photosensitive compositions consisting of azide photosensitive material and epoxy resin (US Pat. No. 2,852,379), and polyvinyl cinnamate, which contain inorganic compounds in the molecule. Photosensitive resins that have saturated double bonds and become insolubilized by a doubling reaction upon irradiation with actinic rays, such as British Patent No.
Derivatives of polyvinyl cinnamate described in specifications such as No. 843545, No. 966297, and U.S. Patent No. 2,725,372, bisphenol A and divanyl, as described in Canadian Patent No. 696,997. cyclohexanone, photosensitive polyesters formed by condensation of p-phenylene diethoxy acrylate and 1,4-di-β-hydroxyethoxycyclohexanone, prepolymers of diallyl phthalate as described in U.S. Pat. No. 3,462,267, etc. and at least two unsaturations in the molecule
Ethylenically unsaturated compounds that have a double bond and cause a polymerization reaction when irradiated with actinic rays, such as unsaturated esters of polyols such as those described in Japanese Patent Publication No. 35-8495, such as ethylene di(meth)acrylate , diethylene glycol di(meth)acrylate, glycerol di(meth)acrylate, glycerol tri(meth)acrylate, ethylene dimethacrylate, 1,3-propylene di(meth)acrylate, 1,4-cyclo-
Hexanediol (meth)acrylate, 1,4
-Benzenediol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,3-propylene glycol di(meth)acrylate, 1,5-pentadiol di(meth)acrylate
Acrylate, pentaerythritol tri(meth)
Acrylates, bisacrylates and methacrylates of polyethylene glycols with molecular weights from 50 to 500, unsaturated amides, especially amides of α-methylenecarboxylic acids and especially α,ω-diamines and ω-diamines with oxygen present in the middle, such as methylene bis(meth) ) acrylamide and diethylenetriamine tri(meth)acrylamide, divinyl succinate, divinyl adipate, divinyl phthalate, divinyl terephthalate, divinylbenzene-1,3-disulfonate, etc. with a suitable binder such as polyvinyl alcohol or a derivative of cellulose with a carboxy group in the side chain. For example, a photosensitive composition containing polyvinyl hydrogen phthalate, carboxymethyl cellulose, or a copolymer of methyl methacrylate and methacrylic acid becomes insoluble by the action of actinic rays and is used as a negative working type photosensitive composition. Useful. U.S. Patent No. 3635709, U.S. Patent No. 3061430, U.S. Pat.
3061120, o-diazooxide-based photosensitive materials, phosphotungstates of diazo resins (Japanese Patent Publication No. 39-7663), yellow blood salts of diazo resins (US Pat. No. 3,113,023), and diazo resins. Resin and polyvinyl hydrogen phthalate
No. 23684) and the like are useful as positive working type photosensitive materials. Also, U.S. Patent No. 3081168, U.S. Patent No. 3486903, U.S. Patent No. 3512971,
Also useful are photosensitive compositions containing a linear polyamide and a monomer having an addition polymerizable unsaturated bond, as described in various specifications such as No. 3,615,629. If necessary, a surface treatment with a silicate is carried out before coating to increase the hydrophilicity of the surface of the aluminum plate. Preferred silicates include those described in U.S. Patent No.
Those appropriately selected from those described in the specification of No. 2714066 are used. The method for producing a lithographic printing plate support according to the present invention will be explained in more detail below based on Examples. Note that % indicates weight %. Example 1 An aluminum sheet with a purity of 99.5% was grained using a pumice stone-water suspension and a rotating nylon brush roller so that the surface roughness Ra = 0.6 microns, and then the aluminum was grained using a 20% aqueous solution of caustic soda. Etching was performed so that the dissolved amount was 8 g/m ² . After thoroughly washing with running water, the substrate was pickled with a 25% nitric acid aqueous solution, and a water-washed board was prepared. The surface of this substrate was electrolytically roughened using an alternating current waveform using a rectangular wave as shown in FIG. 3 under the conditions shown in Table 1 below.
Subsequently, the surface was cleaned by immersion in a 15% sulfuric acid aqueous solution at 50°C for 3 minutes, and then anodized by direct current in a 20% sulfuric acid aqueous solution to form an oxide film of 2.4 g/ ^m2 . C and D were created. The following photosensitive layer was provided on the sample prepared in this way so that the coating amount after drying was 2.5 g/m ² . Ester compound of naphthoquinone-1,2-diazido-5-sulfonyl chloride and pyrogallol ascent resin (described in Example 1 of US Pat. No. 3,635,709) 0.79 g Cresol novolac resin 2.00 g Oil Blue #603 (Orient Chemical ) 0.04 g Ethylene dichloride 16 g 2-methoxyethyl acetate 12 g The photosensitive lithographic printing plate thus obtained was exposed imagewise for 60 seconds from a 3 kW metal halide lamp at a distance of 1 m, and the SiO ₂ /Na ₂ O molar ratio was 1.2. ₂ was developed with an aqueous sodium silicate solution containing 1.5%. When the lithographic printing plate thus obtained was used for printing according to a conventional procedure, the results shown in Table 2 below were obtained. From these results, it was found that lithographic printing plates produced using an electrolyte to which sulfuric acid was added within the scope of the present invention had a longer printing life than those without sulfuric acid and when sulfuric acid was added beyond the scope of the present invention. It can be seen that it has excellent performance in terms of resistance to staining.

【table】

[Table] Example 2 A pumice stone-water suspension with an average particle size of 100 microns was mixed with water being discharged from a nozzle at a pressure of 50 kg/cm ² on a JISA1050 aluminum sheet, and the surface was roughened by colliding with the aluminum surface. A grain of Ra = 0.5 micron was created over the entire surface of the aluminum plate. The amount of etching on this surface is 5g/m ²
It was etched using a 20% aqueous solution of caustic soda so that Etching was performed using an aqueous solution. After washing with water, the substrate was pickled in a 20% nitric acid aqueous solution and washed with water to prepare a substrate. The surface of this substrate was electrolytically roughened using a rectangular alternating waveform current and a sinusoidal alternating waveform current shown in FIGS. 3 and 4, respectively, under the conditions shown in Table 3 below. After washing with water, the surface was cleaned by immersing it in an aqueous solution of 15% sulfuric acid at 50°C. Afterwards, it was anodized by direct current in a 20% sulfuric acid aqueous solution to give a yield of 1.8 g/ ^m2.
An oxide film was provided. Next, it was immersed in a 1% aqueous sodium silicate solution at 70°C for 1 minute, washed with water, and dried. In this way, samples E, F, G, and H were prepared with only the electrolytic surface roughening conditions different.
SEM images of the roughened surfaces of Samples E and F were
This is shown in Figure A and Figure 7B. A photosensitive solution with the following composition was applied to the sample prepared in this way so that the dry weight was 2.0.
The coating was carried out so that the amount was 1.2 g/m ² . Photosensitive liquid N-(4-hydroxyphenyl)methacrylamide/2-hydroxyethyl methacrylate/
Acrylonitrile/methyl methacrylate/methacrylic acid (=15:10:30:38:7 molar ratio) copolymer (average molecular weight 60,000) 5.0g Hexafluorophosphate of condensate of 4-diazodiphenylamine and formaldehyde 0.5g Phosphorous acid 0.05g Victoria Pure Blue BOH (Hodogaya Chemical
Co., Ltd.) 0.1g 2-methoxyethanol 100g The photosensitive lithographic printing plate made in this way,
Pass a transparent negative film through a vacuum printing frame,
Fujifilm PS light (Toshiba metal halide lamp, MU2000-2-DL type 3kW) from a distance of 1m
After exposure for 50 seconds using a light source (available from Fuji Photo Film Co., Ltd.),
It was developed with a developer having the composition shown below, and gummed with an aqueous gum arabic solution to prepare a lithographic printing plate. Developer Sodium sulfite 5g Benzyl alcohol 30g Sodium carbonate 5g Sodium isopropylnaphthalene sulfonate
12 g Pure water 1000 g When the lithographic printing thus obtained was used for printing according to a conventional procedure, the results shown in Table 4 below were obtained. From this result, it can be seen that the lithographic printing plate manufactured using the electrolyte to which sulfuric acid is added within the scope of the present invention has a longer printing life than the plate manufactured using the electrolyte that is outside the scope of the present invention.
It can be seen that it has good performance in terms of resistance to staining, and in particular, excellent printing performance can be obtained when a rectangular alternating waveform current is used.

【table】

[Table] Example 3 Sulfuric acid was added under the electrolytic conditions corresponding to point A in Figure 1.
A 99.5% pure aluminum sheet containing 10 ppm or 500 ppm and pre-treated as described in Example 1 was electrolytically roughened using an alternating waveform current using a square wave under the conditions shown in Table 5 below. Subsequently, the surfaces were cleaned by immersion in a 15% sulfuric acid aqueous solution at 50°C for 3 minutes, and then anodized by direct current in a 20% sulfuric acid aqueous solution to form an oxide film of 1.8 g/m ² . Created. A photosensitive layer was provided on the sample thus prepared as described in Example 1, and the sample was exposed and developed. When the thus obtained lithographic printing plates were used for printing according to conventional procedures, the results shown in Table 6 below were obtained. From these results, it can be seen that the lithographic printing plate manufactured using the electrolyte to which sulfuric acid is added within the scope of the present invention has a longer printing life than the case where the electrolyte solution outside the scope of the present invention is used.
It can be seen that it has good performance in terms of resistance to staining.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of electricity and the reflection concentration in a nitric acid electrolyte. FIG. 2 is a diagram showing changes in reflection density when the amount of electricity is kept constant and the amount of sulfuric acid added is varied. FIG. 3 is a voltage waveform diagram of a current obtained as an asymmetrical alternating waveform current. FIG. 4 is a voltage waveform diagram of a current obtained as a sinusoidal alternating waveform current. Figure 5A, Figure 5B, Figure 5C
The figure is an electron micrograph of a sample obtained by varying the amount of electricity using a nitric acid electrolyte. Figure 6A,
Figures 6B, 6C, and 6D are electron micrographs of samples obtained by varying the amount of sulfuric acid added. FIGS. 7A, 7B, and 8A are electron micrographs of other samples obtained by changing the electrolytic roughening conditions.

Claims (1)

[Claims] 1. Lithographic printing characterized by electrochemically roughening the surface of an aluminum plate with an electrolytic solution containing 1,000 to 40,000 ppm of nitric acid, 50 to 4,000 ppm of sulfuric acid, and other unavoidable impurities. Method for manufacturing plate support. 2 The electrolytic surface roughening is performed using an asymmetrical alternating waveform current until the ratio of the amount of electricity at the cathode to the amount of electricity at the anode is 0.4 to 0.4.
1.25. 1.25. 3 Lithographic printing characterized by electrochemically roughening the surface of an aluminum plate with an electrolytic solution containing 1000 to 40000 ppm nitric acid, 50 to 4000 ppm sulfuric acid, and other unavoidable impurities, and then anodizing the surface. Method for manufacturing plate support. 4. The surface of the aluminum plate is sequentially mechanically roughened, chemically etched so that the dissolved amount of aluminum is in the range of 2 to 12 g/ ^m2 , and
A method for producing a lithographic printing support, which comprises electrochemically roughening the surface using an electrolytic solution containing 40,000 ppm of nitric acid, 50 to 4,000 ppm of sulfuric acid radicals, and other unavoidable impurities.